Various wireless communication technologies are being developed in accordance with advancement of information communication technologies. Wireless communication technologies may be generally classified into technologies using licensed bands and technologies using unlicensed bands (e.g., industrial-scientific-medical (ISM) band) according to bands used by respective technologies. Since a licensed band is exclusively used by a specific operator, the technology using the licensed band may provide better reliability, communication quality, etc. than that using an unlicensed band.
There exists, as a representative cellular communication technology using the licensed band, a Long Term Evolution (LTE) or LTE-Advanced (LTE-A) standardized in a 3rd generation partnership project (3GPP). Thus, a base station or a user equipment (UE) supporting LTE or LTE-A may transmit or receive signals through the licensed band. Also, there exists, as a representative wireless communication technology using the unlicensed band, a wireless local area network (WLAN) defined in IEEE 802.11. Thus, an access point or a station supporting the WLAN may transmit or receive signals through the unlicensed band.
Meanwhile, as mobile traffics are increasing explosively, additional licensed bands are required in order to process such the increasing mobile traffics through licensed bands. However, licensed bands are limited resources. Since a licensed band is obtained usually through an auction held among operators, astronomical investment may be demanded for obtaining the additional licensed bands. In order to resolve the above-described problem, a method for providing LTE or LTE-A services through the unlicensed band may be considered.
In the case that LTE or LTE-A services are provided through the unlicensed band, it may be necessary to coexist with a communication node (e.g., access point, station, and so on) supporting WLAN. For coexistence in the unlicensed band, a communication node (e.g., base station, UE, and so on) supporting LTE or LTE-A may use the unlicensed band based on listen before talk (LBT), and so on. In this case, the communication node supporting LTE or LTE-A may not transmit a signal in desired time. In addition, interferences between a signal which is transmitted from the communication node supporting LTE or LTE-A and a signal which is transmitted from the communication node supporting WLAN may be generated in the unlicensed band. Therefore, for coexistence in the unlicensed band, it is necessary for methods for transmitting and receiving a signal.
Meanwhile, this description on the related arts is written for understanding of the background of the present disclosure. Thus, information on other than conventional technologies, which are already known to those skilled in this technology domain to which the technologies of the present disclosure belong, may be included in this description.